Screen plate for paper making machines



' sept. 24, 1935.

SCREEN PLATE FOR PAPERMAKING MACHINES Filed May 3, 1954 2 Sheeg-v-Svheet 1 llLl Il 161 mare-fr.

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l Sept. 24, 1935. F. DUSTAN SCREEN PLATE FOR PAPER MAKING MACH-INES 2 sheets-'sheet 2 Filed May 5, 1954 1L, WL F 1r -Lw ..IF e a @i d WH NN. m, he. MNM, j A l f Il A s. v Awl/ .V mw f Patented Sept. 24, 51935 PATENT OFFICE SCREEN PLATE FOR PAPER MAKING MACHINES Frank Dustan, Fitchburg, Mass., assignor to William A. Hardy & Sons Co., Fitchburg, Mass., a corporation of Massachusetts Application May s, 1934, serial No. 723,159 3` claims. ,(cl. s2- 30) The principal objects of this invention are to provide a screen plate adapted to be used in the ordinary way, the screening surfaces of which can be made of thin sheets of stainless steel and to 5 make the plate in sections obtaining the rigidity from the sheet metal itself by shaping the edges of the sections down to a vertical position, thereby eliminating the supporting grid or framework formerly employed to support the thin top sheet l on this built up type of screen, thus providing a very rigid plate with less material and less cost.

A further object is to provide a screen plate without surfaces directly adjacent to the under side of the narrow screening slits, such as those l formed in the ordinary thicker type of bronze screen plate, and between which the-screened pulp often collects and clogs, necessitating the removal and cleaning of the plate.

Other objects and advantages of the invention 20 will appear hereinafter.

Reference is to be had to the accompanying drawings, in which Fig. 1 is a plan of a screen plate constructed in accordance with this invention;

.25I Fig. 2 is an end View as indicated by the arrowl 2 in Fig. 1;

Fig. 3 is a similar view of a short piece of metal used on the end section;

Fig. 4 is a sectional view on the line 4--4 of 30 Fig. l;

Fig. 5 is an elevation of the cross truss used on the bottom of the plate;

Fig. 6 is a plan of a modified form; Fig. 7 is a side view of the same, as indicated 35 by the arrow 1 in Fig. 6, partly in section;

Fig. 8 is an end view as indicated by the arrow 8 in Fig. 6;

Fig. 9 is a plan of another modified form;

Fig. 10 is a sectional view on the line Ill-ill 40 of Fig. 9, and

Fig. 11 is an end view as indicated by the arrow l l in Fig. 9. v

In using a screen plate the pulp flows over the screen and is drawn through the slots by means of a diaphragm', not shown. The bronze scrueens heretofore commonly used have been of considerable thickness, about three-eighths of an inch, in order to give them the requisite strength. A series of channels o'r grooves are milled on the 50 under side of the plates, the depth :of these lgrooves extending very nearly to the upper surface of the plate. These grooves are of considerable width at the under surface, tapering or decreasing in Width as they extend up into the plate. Fine slits are cut through from the bottom of these grooves to the topy surface of the plate, through which the pulp is screened. The function of the metal of the lower portion of the plate between the milledchannels is merely to strengthen or sustain the upper slitted screening 5 surface.

'Ihe said milled channels are made tapering. and broadest at the lower surface of the plate in order that the pulp, after having passed through the narrow slits, may fall away freely; l0 but in practice it is found that the pulp often collects and clogs in these channels, necessitating theremoval and cleaning of theplates in-r volving a considerable loss of time and also additional wear and tear on the plates due to l5 the cleaning operation.

I am aware that several attempts have-been made to construct a screen plate of a thin slittedmetal sheet, supported on an open frame having rectangularopenings similar to those of a window sash, and having no surfaces or obstructions directly adjacent to the under side of the narrow screening slits. Such a screen plate is shown in Pinder and Hardys United States Patent No. 234,719 of November 23, 1880. These 25 built up types of screens have not been commer-- cially successful due chieiiy to the difliculty ofl making and maintaining an intimate contact bef tweenthe thin top sheet and the numerous cross bars of the frame or grid upon which the sheet is supported.

My new construction provides a screen plate free from obstructions on the under side adjacent to the fine slots, and in which the principal supporting or st-iiening members are integral with the top sheet, thereby eliminating the sep.-` arate framework or grid as heretofore used in this built up type of screen plate.

This is done by making the plate of a series of sections of stainless sheet steel or other rust- -40 less materialv shaped or drawn into a form in which the edges are bent downwardly to form a margin around or along each section and provide vertical flanges which will stiien the sections. employed and the efliciency increased in the manner just stated.

Referring to the first sheet of drawings, a screen plate is shown composed of four screen channel sections of sheet stainless steel or other y50 material I0 having side anges Il bent from each section downwardly for strengthening purposes. The anges of each adjacent two sections are spot-welded together throughout their length at I2.

Thus a smaller amount of metal can be Fig. 4 shows an intermediate cross truss I3 between the ends of the sections. This truss is machined out at I4 to fit snugly over the channel flanges, as shown. Several of these intermediate trusses are welded in place. Side sills I5 extend throughout the length of the screen on both sides and are spot-welded to the assembled channel flanges. It is by means of these sills that the screen plates are provided with enough metal to enable them to be fastened to the vats by means of screws or the like, not shown. Short pieces I6 of solid metal are fltted and welded into the channels lat each end of the screen plate to reinforce the ends and support the screws or other means by which the ends of the screen are fastened in the vats.

Before the strips of stainless steel composing the channels are formed in the channel shapes they are provided with thin slits I1 by means of saws operating on the arcs I8.

By constructing a screen plate, as shown in these figures, all under side joints have been practically eliminated. The only under side joints existing are located between the intermediate cross trusses I3 and the under side of the channels and between the short reinforcing end pieces I6 and the channels. These pieces I3 and I6 are easily fitted snugly in place. As the top sheet is stiffened by being channeled, that is, by providing it with its side flanges, these top sheets by the two means are rendered free of any tendency to warp out of a flat plane. Therefore, no difficulty is encountered in obtaining and maintaining a contact between these sheets 4Ill and the short under side pieces.

Referring to the form shown in Figs. 6, 7 and 8, this screen plate is composed of a series of pressed stainless steel trays 20 having downwardly extending flanges 2| and 22 integral with the top and each other at the corners and vertical. These flanges of different trays are spot-welded together along adjacent vertical surfaces. 'I'he side sills 23 are spot-welded to the other flanges of the assembled trays. The end sills 24 are similarly welded to the ends of the trays along their flanges. 'I'hese sills receive the screws or other means used for fastening the screen plates into the vats. Before the sheets composing the screen are formed into the tray shape, they are slotted as indicated at 25 in the same manner as is illustrated in the first sheet.

This construction is entirely free from any under side joints. The under side of each inverted tray presents an unbroken smooth surface, not allowing the pulp to catch on any vertical or inclined surface in a position where it can be held until it is dislodged.

Inthe form shown in Figs. 9, 10 and 11 the screen plate is composed of a series of stainless steel Wide short channel sections 30. 'I'hese channel sections are assembled and spot-welded to cross strips 3|, which act as butt straps and also form cross trusses in the assembled screen. The 5 side sills 32 are spot-welded to the assembled channel flanges. The end sills 33 are fltted to the under sides of the end sections and spot- Welded to them. These sills receive screws or other means used to fasten the screen plates to 10 the vats. Before the sheets composing the screen are formed into the wide, short channel sections they are slitted, as indicated at 34, inthe same way as has been described above.

This construction has only the short cross l5 members 3| and 33 which have to be brought into intimate contact with the under side of the wide short sections 30 and these short, separate members 3| and 33 can easily be individually fitted in close contact with the top sheet. These joints are 20 spot-welded all over.

The construction of a screen made up of sections of stainless sheet steel or other material, previously slitted, and having side or end flanges, or both side and end flanges, to strengthen them 25 is a distinct advance in this art. A lighter and at the same time more rigid plate is provided and the under side faults present in former constructions have been eliminated.

Having thus described my invention and the 30 advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but what I claim is:-

1. A screen plate comprising a series of longitudinal sections of slitted sheet material hav- 35 ing integral, vertical, downwardly extending side flanges spot welded together, side sills welded to the outer side flanges, and filling blocks Welded into the end of each section between its flanges.

2. As an article of manufacture, a screen plate 40 consisting of a series of trays of sheet material slitted on top and each having a downwardly extending continuous flange all around it, and each extending across the screen plate, the adjacent transverse flanges being spot welded together, side sills spot welded to the longitudinal flanges, and end sills spot welded to the two end transverse flanges.

3. A screen plate comprising a series of slitted metal sheets having side and end edges turned down to form strengthening flanges, said flanges being integrally connected at the corners of the plate, each formed sheet being secured to the next one along the flat vertical sides of two adjacent flanges, and a surrounding frame for use in securing the screen plate in a vat.

FRANK DUSTAN. 

